CN109734718B - Polycarboxylic acid organic ligand based on NDHPI modification and synthetic method - Google Patents

Abstract

The invention relates to a polycarboxylic acid organic ligand based on NDHPI modification and a synthetic method thereof. Belongs to the technical field of organic chemical synthesis. Coupling 3, 6-dibromotetramethylbenzene with phenylboronic acid with methyl at 4-position or 3, 5-position on a benzene ring under the catalysis of palladium to obtain a terphenyl compound containing multiple methyl, oxidizing methyl by potassium permanganate at 90-110 ℃ by using pyridine and water as solvents to generate a structure of polycarboxylic acid terphenyl, directly reacting the polycarboxylic acid terphenyl compound with hydroxylamine hydrochloride in a pyridine solution at 100 ℃ for 5 hours, cooling, removing the solvent by spinning, adding water and hydrochloric acid to adjust the pH to 1 to separate out a large amount of precipitates, centrifuging, washing with water, and drying to obtain a pure target product with high yield. Compared with the traditional process, the method has the advantages of simple process and high product purity. The MOFs material prepared by the method has wide application prospect in the field of catalysis due to the excellent comprehensive properties of 94-99% of the MOFs material, such as high catalytic efficiency, recycling property and the like.

Description

Polycarboxylic acid organic ligand based on NDHPI modification and synthetic method

Technical Field

The invention relates to a polycarboxylic acid organic ligand based on NDHPI modification, and further relates to a synthetic method of the polycarboxylic acid ligand, belonging to the technical field of organic chemical synthesis.

Background

NDHPI is the abbreviation for N, N' -dihydroxypyromellitic acid imine. The N, N' -dihydroxy pyromellitic acid imine (NDHPI) is an ideal green oxidant and is widely applied to oxidation reactions of aromatic hydrocarbon, alkane, alkene, alkyne, alcohol, ether, amide and acetal as an electrochemical oxidation matrix or catalyst, and the NDHPI is widely concerned and applied in the field of molecular oxygen oxidation due to the simple preparation process, the double-site active group and the high-activity catalytic property. However, as homogeneous small molecular catalysts, N, N' -dihydroxy pyromellitic acid imine (NDHPI) and analogues thereof and N-hydroxyphthalimide (NHPI) and analogues thereof, which are also the same as other small molecular catalysts, have the problems of incapability of recycling, increased difficulty in post-reaction treatment and the like.

In order to solve such problems, related researchers have attempted to immobilize NDHPI containing two N-hydroxyl active sites on the surface of some specially prepared solid materials by chemical synthesis, thereby imparting the NDHPI with heterogeneous characteristics. For example, Lestacin et al tried to prepare a supported catalyst by supporting NDHPI as a New composite catalyst for cellulose aerobiotic oxidation, catalysts Letters,2017,147(4):856-864) on SBA-15 by chemical grafting method. Although the method realizes the immobilization of NDHPI, one N-hydroxyl in the structure of NDHPI is used as a reaction site for connection, so that half of catalytic sites are destroyed while the immobilization is realized, and the catalytic effect is greatly reduced. In addition, N '-dihydroxy pyromellitic acid imine (NDHPI) has two unsubstituted vacant sites on the benzene ring difficult to generate chemical reaction due to the strong electron withdrawing effect of four carbonyl groups, so that the N, N' -dihydroxy pyromellitic acid imine (NDHPI) is difficult to modify and carry on the premise of ensuring that two N-hydroxyl active sites are not damaged.

In view of inherent porosity and excellent recycling performance of metal organic framework Materials (MOFs), related researchers limit NDHPI of small molecules in channels of the metal organic framework Materials (MOFs) to realize performance research of heterogeneous catalysis under the condition that catalytic sites are not damaged at all. For example, Oleksii Pliekhov et al utilize Co-MOF-74 to perform a domain-limiting effect on NDHPI, so as to fix The NDHPI in The pore channels of The MOFs material, thereby achieving The purpose of heterogeneous Catalysis (The Co-MOF-74modified with N, N' -Dihydropyro millitimetric for selective, solvent free aerobic oxidation of cellulose, Catalysis Communications, 110 (2018): 88-92). However, this method cannot confine the NDHPI completely in its pore channels, and the NDHPI will leak continuously during the catalytic process, resulting in poor recycling and difficulty in achieving the target catalytic effect.

Considering the problem of limited domain leakage, a method for directly realizing N-hydroxyl functionalization on an organic ligand is discovered shortly before, and the problem of reusability is better solved by introducing an NHPI functional group containing a single active site in a covalent bond form in the synthesis process of the organic ligand and then preparing a metal organic framework Material (MOFs) based on the NHPI functionalized polycarboxylic organic ligand and the synthesis method thereof (Chinese patent application No. 201811376621.4). However, compared with the symmetric structure of NDHPI, NHPI only contains a single active site capable of generating nitroxide free radicals, and the catalytic activity is relatively low, so that in practical application, the MOFs material prepared by NHPI functionalized ligand has larger dosage, higher reaction temperature and longer reaction time, which is very disadvantageous for realizing the reusability of the MOFs material.

Disclosure of Invention

The invention aims to provide a polycarboxylic acid organic ligand which can be used for preparing a series of functional materials which are three-dimensionally porous and have a large number of N, N' -dihydroxy pyromellitic acid imine (NDHPI) structural units exposed in pore channels. The metal organic framework Materials (MOFs) prepared by the ligand have good catalytic effect and can be repeatedly utilized. Another purpose of the invention is to disclose a method for synthesizing the ligand.

In order to achieve the purpose, the invention starts from the functional design of an organic ligand, and directly introduces N, N' -dihydroxy pyromellitic acid imine (NDHPI) into a polycarboxylic acid organic ligand for constructing a porous framework material by an organic synthesis method, so that metal organic framework Materials (MOFs) prepared by the ligand not only are rich in active catalytic sites in pore channels, but also can stably exist for a long time by functional groups connected by covalent bonds, and the problems of complete retention and recycling of the catalytic active sites are solved at the same time.

The invention aims to synthesize a polycarboxylic acid organic ligand which can be used for preparing three-dimensional porous and can directly expose N, N' -dihydroxy pyromellitic acid imine groups with catalytic activity in pore channels in a covalent bond mode. The structural formula of the N, N' -dihydroxy pyromellitic imine modified polycarboxylic acid organic ligand is approximately as follows:

in the formula (I), the compound is shown in the specification,^\COOH is mono-COOH or di-COOH;

wherein: mono-COOH is at the 4-position on the phenyl ring; bis-COOH is at two meta positions on the phenyl ring; the concrete structure is as follows:

the above (a) is 4,4' - (2, 6-dihydroxy-1, 3,5, 7-tetraoxo-1, 2,3,5,6, 7-hexahydropyrrolo [3,4-F ] isoindole-4, 8-diyl) dibenzoic acid.

The above-mentioned (b) is 5,5' - (2, 6-dihydroxy-1, 3,5, 7-tetraoxo-1, 2,3,5,6, 7-hexahydropyrrolo [3,4-F ] isoindol-4, 8-diyl) diisophthalic acid.

The preparation method of the polycarboxylic acid organic ligand based on NDHPI modification comprises the following steps: firstly, weighing 3, 6-dibromo-tetramethylbenzene according to a molar ratio: methylbenzeneboronic acid: palladium catalyst: inorganic base: deionized water 1:2:0.03:4:0.05, which was added to an organic solvent in N₂Heating under protection at the temperature of 100-120 ℃, wherein the reaction time is 8-12h, and directly filtering and drying a target product separated out from the solvent after the reaction is finished; and then according to the single methyl on the polymethyl compound: weighing the two according to the molar ratio of 1:6, adding the two into a mixed solution of pyridine and deionized water in equal proportion, heating to 90-110 ℃, and reacting for 15-20h to oxidize methyl; after the reaction is finished, filtering, removing pyridine by spinning, and adding diluentAcidifying with hydrochloric acid, and drying to obtain polycarboxylic acid product; and finally, placing the dried polycarboxylic acid product and hydroxylamine hydrochloride into an organic solvent pyridine solution for heating reaction, wherein the polycarboxylic acid product is as follows: the hydroxylamine hydrochloride is in a molar ratio of 1:2.5, the reaction temperature is 100 ℃, and the reaction time is 5 hours; after the reaction is finished, the solvent is removed by spinning, diluted hydrochloric acid is added for acidification, and the final N, N' -dihydroxy pyromellitic acid imine (NDHPI) modified polycarboxylic acid organic ligand is obtained after centrifugation, water washing and drying;

the methyl phenylboronic acid is phenylboronic acid with methyl at the 4-position or 3, 5-position on a benzene ring;

the palladium catalyst is palladium tetratriphenyl phosphine;

the inorganic base is sodium carbonate;

the organic solvent is 1, 4-dioxane;

the dilute hydrochloric acid used for acidifying the dilute hydrochloric acid is 1mol/L dilute hydrochloric acid solution;

the concrete post-treatment of the last step of reaction is to spin dry the pyridine solution, add 1mol/L diluted hydrochloric acid solution, ultrasonically process for a moment, centrifuge, wash with water, and dry to obtain the N, N' -dihydroxy pyromellitic imine (NDHPI) modified polycarboxylic acid organic ligand.

The invention has the following advantages and beneficial effects:

1. in view of the excellent molecular oxygen oxidation performance of N, N '-dihydroxy pyromellitic acid imine (NDHPI), the invention firstly tries to introduce N, N' -dihydroxy pyromellitic acid imine groups with free radical activity into a polycarboxylic acid organic ligand which can be used for synthesizing a three-dimensional porous material, thereby realizing the direct functionalization of the organic ligand; experimental results show that the metal organic framework Materials (MOFs) prepared by the ligands have good molecular oxygen oxidation performance and excellent reusability.

2. According to the invention, through the research of the design of a large number of process experimental routes, the process synthetic methods such as simple and reasonable raw material proportion and the like are found out, the yield of each step in the reaction process is as high as 83-97%, and the N, N' -dihydroxy pyromellitic acid imine group (NDHPI) functionalization of the polycarboxylic acid organic ligand is successfully realized for the first time through the introduction of four methyl groups on the middle benzene ring of terphenyl.

3. The method finally utilizes the generated structural unit with pyromellitic acid to directly react with hydroxylamine hydrochloride to obtain the imine functional group of N, N' -dihydroxy pyromellitic acid, and compared with the traditional process, the method omits the steps of firstly dehydrating dicarboxylic acid into anhydride and then reacting with hydroxylamine hydrochloride, which are required by the general reactions, simplifies the process, greatly improves the purity of the product, can reach 97 percent, and is very important for polycarboxylic acid substances which are difficult to purify due to the solubility problem.

4. The invention starts from the structural design of an organic ligand, functional groups of N, N' -dihydroxy pyromellitic acid imine are directly introduced into a polycarboxylic acid ligand, and the synthesized ligand can be used for preparing a series of metal organic framework Materials (MOFs), and the MOFs have wide application prospects in the field of catalysis due to the excellent comprehensive properties of 94% -99% of the MOFs, such as excellent catalytic efficiency, recycling property and the like, so that a new thought and possibility are created in the experimental design for realizing NDHPI heterogeneous catalysis.

5. Compared with a polycarboxylic organic ligand based on NHPI functionalization and a synthesis method, the polycarboxylic organic ligand based on NHPI functionalization has two functional groups in one molecule, so that the dosage of catalytic reaction can be reduced by half, and the reaction temperature and time are relatively loose due to relatively high catalytic activity, and the polycarboxylic organic ligand based on NHPI functionalization and the synthesis method have valuable economic benefits.

Drawings

FIG. 1 shows nuclear magnetic hydrogen spectrum of compound a of the present invention

FIG. 2 shows nuclear magnetic carbon spectrum of compound a of the present invention

FIG. 3 shows nuclear magnetic hydrogen spectrum of compound b of the present invention

FIG. 4 shows nuclear magnetic carbon spectrum of compound b of the present invention

Detailed Description

The invention is further described with reference to the accompanying drawings and the detailed description.

Example 1

Polycarboxylic organic ligands (a) based on N, N' -dihydroxypyromellitic imine (NDHPI) modification: 4,4' - (2, 6-dihydroxy-1, 3,5, 7-tetraoxo-1, 2,3,5, 6)7-hexahydropyrrolo [3,4-F]Isoindole-4, 8-diyl) dibenzoic acid (abbreviated as H)₂L_2N-OH) The specific structure of (A) is as follows:

H₂L_2N-OHthe reaction formula of the synthesis method of (1) is as follows:

preparation of organic ligand of polycarboxylic acid based on modification of N, N' -dihydroxypyromellitic acid imine (NDHPI): in N₂6.5mmol of 3, 6-dibromo-tetramethylbenzene, 13mmol of 4-methyl phenylboronic acid, 26mmol of sodium carbonate, 0.2mmol of tetratriphenyl phosphine palladium, 30ml of 1, 4-dioxane and 5.9ml of deionized water are added into a 100ml three-neck flask under protection, replaced by nitrogen for three times, and then heated to 100 ℃ by an oil bath under magnetic stirring to react for 8 hours. After the reaction is finished, standing at room temperature, and then carrying out suction filtration and drying on solid powder precipitated from the reaction solution to obtain the target product, wherein the yield is 93%. Adding 2mmol of the obtained product, 72mmol of potassium permanganate, 15ml of pyridine and 15ml of distilled water into a 100ml three-neck flask, heating to 95 ℃ by using an oil bath under magnetic stirring, carrying out reaction reflux for 15h, after the reaction is finished, carrying out decompression and spin-off on the organic solvent, adding water, filtering out MnO by using diatomite after ultrasonic reaction for a while₂Adding hydrochloric acid to adjust ph to 1, standing in ice water bath for a moment to precipitate a large amount of needle crystals, filtering, collecting and drying to obtain the polycarboxylic acid product with the yield of 95%. Finally, 1.9mmol of the product of hexacarboxylic acid, 4.75mmol of hydroxylamine hydrochloride and 10ml of pyridine were put into a 50ml single-neck flask, and heated to 100 ℃ with magnetic stirring by an oil bath to react for 5 hours. And (3) after the reaction is finished, carrying out decompression and spin-off on the organic solvent, adding dilute hydrochloric acid, carrying out ultrasonic treatment for a moment, carrying out centrifugal collection and drying to obtain a brick-red product: the yield based on the N, N' -dihydroxypyromellitic imine (NDHPI) modified polycarboxylic acid organic ligand (a) was 97%.

The characterization data and the spectrogram of the product polycarboxylic organic ligand (a) are as follows:

¹H NMR(DMSO-d₆,400MHz):δ13.13(s,2H),10.97(s,2H),8.02(d,J＝8.0Hz,4H),7.62(d,J＝8.0Hz,4H)..¹³C NMR(101MHz,DMSO)δ167.47,161.61,135.99,134.83,131.48,131.07,130.07,128.38.

referring to FIG. 1, since the polycarboxylic acid organic ligand (a) has a symmetrical structure, 4 different hydrogen signals are found by analyzing the structure, a doublet at 7.62PPm in the measured nuclear magnetic hydrogen spectrum corresponds to a hydrogen signal at the meta position of the carboxylic acid on the benzene rings at both ends, a doublet at 8.02PPm corresponds to two hydrogen signals at the ortho positions of the carboxylic acid on the benzene rings at both ends, a single peak at 10.97PPm corresponds to a characteristic signal peak of hydrogen on the nitrogen hydroxyl group, a single peak at 13.13PPm corresponds to a characteristic signal peak of active hydrogen of the carboxylic acid, and the corresponding number ratio of hydrogen atoms is completely consistent with the structure (a) (wherein 2.5PPm and 3.3PPm are respectively a solvent peak and a water peak of deuterium-substituted DMSO used);

referring to FIG. 2, since (a) is a symmetric structure, the analysis of the structure reveals 8 different carbon signals, the observed nuclear magnetic carbon spectrum has 167.47ppm signal peaks corresponding to the carbon signal of carboxylic acid, 161.61ppm signal peaks corresponding to the carbon signal of ketone carbonyl linked to imine, and 6 signal peaks in the range of 128.38-135.99ppm corresponding to the carbon signals of 6 different chemical environments on three benzene rings, respectively (wherein the seven-fold peak at 39.50ppm is the coupling split of the carbon signal of deuterated DMSO used);

example 2

N, N' -dihydroxypyromellitic imine-modified polycarboxylic acid organic ligand (b): 5,5' - (2, 6-dihydroxy-1, 3,5, 7-tetraoxo-1, 2,3,5,6, 7-hexahydropyrrolo [3,4-F ]]Isoindole-4, 8-diyl) diisophthalic acid (abbreviated as H)₄L_2N-OH) The specific structure of (A) is as follows:

H₄L_2N-OHthe reaction formula of the synthesis method of (1) is as follows:

preparation of polycarboxylic acid organic ligand (b) based on modification of N, N' -dihydroxypyromellitic acid imine: in N₂6.5mmol of 3, 6-dibromotetramethylbenzene, 13mmol of 3, 5-dimethylphenylboronic acid, 26mmol of sodium carbonate, 0.2mmol of tetratriphenylphosphonium palladium, 30ml of 1, 4-dioxane and 5.9ml of deionized water are added into a 100ml three-neck flask under protection, replaced by nitrogen for three times, and then heated to 120 ℃ by an oil bath under magnetic stirring for reaction for 12 hours. After the reaction is finished, standing at room temperature, and then carrying out suction filtration and drying on solid powder precipitated from the reaction solution to obtain the target product, wherein the yield is 91%. Adding 2.5mmol of the obtained product, 120mmol of potassium permanganate, 25ml of pyridine and 25ml of distilled water into a 250ml three-neck flask, heating to 110 ℃ by using an oil bath under magnetic stirring, carrying out reaction reflux for 20 hours, after the reaction is finished, carrying out decompression and rotary removal on an organic solvent, adding water, filtering MnO by using diatomite after ultrasonic reaction for a moment₂Adding hydrochloric acid to adjust ph to 1, standing at room temperature to precipitate a large amount of white powder, centrifuging, collecting and drying to obtain the polycarboxylic acid product with the yield of 83%. Finally, 1.8mmol of octacarboxylic acid product, 4.5mmol of hydroxylamine hydrochloride and 10ml of pyridine were put into a 50ml single-neck flask, heated to 100 ℃ with magnetic stirring by an oil bath, and reacted for 5 hours. And (3) after the reaction is finished, carrying out decompression and spin-off on the organic solvent, adding dilute hydrochloric acid, carrying out ultrasonic treatment for a moment, carrying out centrifugal collection and drying to obtain a yellow product b, wherein the yield is 92%.

The characterization data for this product are as follows:

¹H NMR(600MHz,DMSO-d₆)δ13.42(s,4H),11.02(s,2H),8.60(s,2H),8.31(s,4H).¹³C NMR(151MHz,DMSO)δ166.73,161.97,135.04,133.63,132.29,131.73,130.70,130.42.

referring to FIG. 3, since (b) is a symmetrical structure, 4 different hydrogen signals are found by analyzing the structure, and the measured nuclear magnetic hydrogen spectrum has a single peak at 8.31PPm corresponding to four hydrogen signals at the ortho positions of the carboxylic acids on the benzene rings at both ends, a single peak at 8.60PPm corresponding to a signal of hydrogen in the middle of two carboxyl groups at both ends, a single peak at 11.02PPm corresponding to a characteristic signal peak of hydrogen on the nitrogen hydroxyl group, a single peak at 13.42PPm corresponding to a characteristic signal peak of active hydrogen of the carboxylic acid, and the number ratio of corresponding hydrogen atoms completely agrees with the structure (b) (wherein 2.5PPm and 3.3PPm are a solvent peak and a water peak of deuterated DMSO used, respectively);

referring to FIG. 4, since (b) is a symmetric structure, the analysis of the structure reveals 8 different carbon signals, the observed nuclear magnetic carbon spectrum has 166.73ppm signal peaks corresponding to the carbon signal of carboxylic acid, 161.97ppm signal peaks corresponding to the carbon signal of ketone carbonyl linked to imine, and 6 signal peaks in the range of 130.42-135.04ppm corresponding to the carbon signals of 6 different chemical environments on three benzene rings, respectively (wherein the seven-fold peak at 39.50ppm is the coupling split of the carbon signal of deuterated DMSO used);

example 3

According to the following steps: 1.2: weighing the ligand (a) and ZrCl at a molar ratio of 30₄Benzoic acid is put into a glass bottle, then N, N' -Dimethylformamide (DMF) solution and a drop of deionized water are added, the solution is clarified by ultrasonic treatment for 10 minutes, then the solution is put into a constant-temperature oven at 70 ℃ for reaction for 2 days, then the temperature is raised to 85 ℃ for one day, finally the temperature is raised to 100 ℃ for reaction for 2 days, after the reaction is stopped, the obtained white powder precipitate is washed by DMF, then is soaked by acetone for 3 days, and is activated in vacuum at 120 ℃ for 12 hours, and the crystal yield is about 76% based on the ligand. PXRD test results show that the obtained white powder has good crystallinity, SEM scanning results show that the obtained white powder is of a nano-scale regular octahedral structure with uniform size, and BET test results show that the specific surface area of the obtained material is 1470.2046m².g^-1Thus proving the success of preparing the target metal-organic framework material MOFs (UiO-68-2 nhpi). The MOFs (UiO-68-2nhpi) obtained was used again as heterogeneous catalyst, O₂The catalyst is used as an oxygen source to oxidize primary alcohol and secondary alcohol, and experimental results prove that a series of primary alcohol and secondary alcohol with 1 equivalent can be oxidized to corresponding aldehyde and ketone by 5 percent equivalent of UiO-68-2nhpi and a proper amount of initiator under the oxygen atmosphere with 1 atmosphere pressure, the oxidation yield can generally reach more than 95 percent through detection, and the experimental results show that the obtained UiO-68-2nhpi can be reused for 6 times and still has good catalytic effect.

Comparative example: except that the ligand (a) (abbreviated as H)₂L_2N-OH) Replacement to an organic ligand based on NHPI functionalization of polycarboxylic acids: 4,4' - (2-hydroxy-1, 3-dioxoisoindoline-4, 7-diyl) dibenzoic acid (abbreviated to "H")₂L_N-OH) In addition, the other preparation methods are the same, and the obtained heterogeneous catalyst, O₂As an oxygen source to oxidize primary and secondary alcohols, experimental results show that at least 10% equivalent of NHPI functionalized heterogeneous catalyst is required to oxidize a series of 1 equivalent of primary and secondary alcohols to the corresponding aldehydes and ketones, thus proving that the heterogeneous catalyst prepared from the synthesized NDHPI modified organic ligand of the invention can be used in half in catalytic reaction, and has valuable use economic benefits.

Example 4

According to the following steps: 2.3 molar ratio of ligand (b) to Cu (NO)₃)_2'2.5H₂O in a glass bottle, then adding N, N' -Dimethylformamide (DMF) and ethanol solution according to the ratio of 2:1, and finally adding one drop of HBF₄And (3) carrying out ultrasonic treatment on the mixed solution for 15 minutes to completely dissolve the ligand and the metal salt, then placing the clear solution into a constant-temperature oven at 60 ℃ to react for 24 hours to obtain a blue blocky crystal, washing the obtained blue crystal with DMF, then soaking the blue crystal in acetone for 3 days, and carrying out vacuum activation at 80 ℃ for 10 hours, wherein the crystal yield is about 55% based on the ligand. PXRD test results show that the obtained blue crystal has good crystallinity, SEM scanning results show that the obtained crystal is of an octahedral structure with uniform size, and BET test results show that the specific surface area of the obtained material is 1865.4126m².g^-1Therefore, the successful preparation of the target metal-organic framework material MOFs (NOTT-2nhpi) is proved. The MOFs obtained (NOTT-2nhpi) were then used as heterogeneous catalyst, O₂The NOT-2 nhpi with 7% equivalent weight and a proper amount of initiator can oxidize a series of primary alcohol and secondary alcohol with 1 equivalent weight to corresponding aldehyde and ketone under the oxygen atmosphere of 1 atmospheric pressure, and can oxidize a series of primary alcohol to corresponding carboxylic acid products by properly prolonging the catalytic reaction time, the oxidation yield can reach more than 93% generally through detection, and the experimental result shows that the obtained NOT-2 nhpi can be used repeatedly for 8 times and still can be well maintained.

Comparative example: except that the ligand (b) (abbreviated as H)₄L_2N-OH) Replacement to an organic ligand based on NHPI functionalization of polycarboxylic acids: 5,5' - (2-hydroxy-1, 3-dioxoisoindoline-4, 7-diyl) diisophthalic acid (abbreviated as H)₄L_N-OH) In addition, the other preparation methods are the same, and the obtained heterogeneous catalyst, O₂As an oxygen source to oxidize primary and secondary alcohols, experimental results show that at least 15% equivalent of NHPI functionalized heterogeneous catalyst is required to oxidize 1 equivalent of a series of primary and secondary alcohols to the corresponding aldehydes and ketones or to carboxylic acid products with extended reaction time, thus demonstrating that heterogeneous catalysts prepared from the synthesized NDHPI modified organic ligands of the present invention can be used in catalytic reactions in half with valuable use economics.

Claims (2)

1. An organic ligand based on NDHPI modification of polycarboxylic acid, which is characterized in that: the structural formula of the polycarboxylic acid organic ligand based on NDHPI modification is shown as follows:

in the formula (I), the compound is shown in the specification,^\COOH is mono-COOH or di-COOH;

wherein: mono-COOH is at the 4-position on the phenyl ring (a); bis-COOH is in two meta positions on the phenyl ring (b); the specific structures are respectively as follows:

the (a) is 4,4' - (2, 6-dihydroxy-1, 3,5, 7-tetraoxo-1, 2,3,5,6, 7-hexahydropyrrolo [3,4-F ] isoindole-4, 8-diyl) dibenzoic acid;

the above-mentioned (b) is 5,5' - (2, 6-dihydroxy-1, 3,5,7, -tetraoxo-1, 2,3,5,6, 7-hexahydropyrrolo [3,4-F ] isoindol-4, 8-diyl) diisophthalic acid.

2. AA method of synthesizing the NDHPI-modified polycarboxylic acid organic ligand according to claim 1, characterized in that: firstly, weighing 3, 6-dibromo-tetramethylbenzene according to a molar ratio: methylbenzeneboronic acid: palladium catalyst: inorganic base: deionized water 2:1:0.03:4:0.05, which was added to an organic solvent in N₂Heating under protection at 90-120 deg.C for 8-12h, and directly filtering and drying the separated target product after reaction; and then according to the single methyl on the polymethyl compound: weighing the two in a molar ratio of 1:6, adding the two into a mixed solution of pyridine and deionized water in equal proportion, heating to 90-110 ℃, and reacting for 15-20h to oxidize methyl; after the reaction is finished, filtering, removing pyridine by spinning, adding dilute hydrochloric acid for acidification, and drying to obtain a polycarboxylic acid product; and finally, placing the dried polycarboxylic acid product and hydroxylamine hydrochloride into an organic solvent pyridine solution for heating reaction, wherein the polycarboxylic acid product is as follows: the hydroxylamine hydrochloride is in a molar ratio of 1:2.5, the reaction temperature is 100 ℃, and the reaction time is 5 hours; after the reaction is finished, the solvent is removed by spinning, diluted hydrochloric acid is added for acidification, and the NDHPI modified polycarboxylic acid organic ligand is obtained after centrifugation, water washing and drying;

the methyl phenylboronic acid is phenylboronic acid with methyl at the 4-position or 3, 5-position on a benzene ring;

the palladium catalyst is palladium tetratriphenyl phosphine;

the inorganic base is sodium carbonate;

the organic solvent is 1, 4-dioxane;

the eluent used for the column chromatography is petroleum ether;

the dilute hydrochloric acid used for acidifying the dilute hydrochloric acid is 1mol/L dilute hydrochloric acid solution;

the concrete post-treatment of the last step of reaction is to spin dry the pyridine solution, add 1mol/L diluted hydrochloric acid solution, ultrasonically process for a moment, centrifuge, wash with water, and dry to obtain the polycarboxylic acid organic ligand based on NDHPI modification.

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